Image Processing Toolbox

Selecting Control Points

The toolbox includes an interactive tool that enables you to specify control points in the images you want to register. The tool displays the images side-by-side. When you are satisfied with the number and placement of the control points, you can save the control points.

Using the Control Point Selection Tool

To specify control points in a pair of images you want to register, use the Control Point Selection Tool, cpselect. The tool displays the image you want to register, called the input image, next to the image you want to compare it to, called the base image or reference image.

Specifying control points is a four-step process:

1. Start the tool, specifying the input image and the base image.
2. View the images, looking for visual elements that you can identify in both images. cpselect provides many ways to navigate around the image, panning and zooming to view areas of the image in more detail.
3. Specify matching control point pairs in the input image and the base image.
4. Save the control points in the MATLAB workspace.

Figure 5-2, Control Point Selection Tool shows the default appearance of the tool when you first start it. To get more information about any part of the interface, click on it in this figure.

Figure 5-2: Control Point Selection Tool

Types of Supported Transformations

Starting the Control Point Selection Tool